T.F. Torrance, Trinitarian Faith (T&T Clark, 1995).
"How are we to understand the passion of the incarnate Son of God, when he offered himself and not just his body in vicarious sacrifice for the sins of mankind? What does the suffering of Christ really mean for what he was and is in his own Person as the one Mediator between God and man? There is (184) certainly a sense in which we must think of God as impassible…for he is not subject to the passions that characterize human and creaturely existence, but that is not to say that he is not afflicted in all the afflictions of his people or that he is untouched by their sufferings. If we think of the atonement as taking place within the incarnate constitution of the Mediator who is God and man in one Person, then, as Athanasius argued against the Arians, we cannot think of the sufferings of Christ as external to the Person of the Logos. It is the very same Person who suffered and who saved us, not just man but the Lord as man; but his divine and his human acts are acts of one and the same Person.
The point is this. In Jesus Christ God himself has penetrated into our passion, our hurt, our violence, our condition under divine judgment, even into our utter dereliction…but in such a profoundly vicarious way that in the very heart of it all, he brought his eternal serenity or [apatheia] to bear redemptively upon our passion. Thus we may say of God in Christ that he both suffered and did not suffer, for through the eternal tranquility of his divine impassibility he took upon himself our passibility and redeemed it. In the nature of the case this is not something about which a logical account can be given, for logically impassibility and passibility exclude one another. Rather is it to be understood dynamically and soteriologically on the ground of what has actually taken place in the vicarious life and passion of God’s incarnate Son. Nor can God be thought of as ‘impassible’ in the Greek or Stoic sense, but on the contrary as God who in his measureless love and compassion has stooped to take upon himself our passion, our hurt and suffering, and to (185) exhaust it in his divine impassibility…in such a way that he masters and transmutes it within the embrace of his own immutable peace and serenity. It is an essential aspect of the atoning exchange in Jesus Christ that through his sharing in our passion…he makes us share in his own imperturbability (186)."